a. Field of the Invention
This invention relates generally to telephony, and more particularly to a method and a system for detecting when a party has been added to a pre-existing telephone call.
b. Background Art
Modern phone companies offer a number of convenient services to their customers. One such service is called conference-calling, third-party calling or “three-way” calling. This allows an originating caller and a recipient caller, who establish a conversation, to engage the phone system to dial and connect a third party into the conversation as well.
Three-way calling is a convenient feature in many situations, but poses a problem in others. Inmates in correctional facilities have the ability to originate phone calls to others, but typically are not able to call those numbers on a given inmate's “restricted-number” list. Persons on the restricted list may include judges, prosecutors, other lawyers, victims of the inmate's crimes, or even other family members (especially in the case of protection-from-abuse (PFA) cases). By using three-way calling, inmates are able to contact people on these restricted lists. They first call a number not on the restricted list (a friend, for example), then have the friend perform a three-way call to the restricted number.
Although current prior art and patented devices attempt to solve the three-way call problem, they all suffer from one major limitation; namely, they are not 100% effective at detecting such calls. Inventions such as this are useful in correctional-institutes telephony markets, but some percentage of inmate calls (as much as 10%, 20%, or even 30%) which use three-way calling to get another party on the line, in violation of call-restriction rules, will get past the modern three-way call-detection system undetected and on to the intended party. Commercial pressures exist for the accuracy rates to be higher, and if possible, to be 100% to handle those calls that escape detection by present equipment and techniques.